There are multiple reasons why such a symptom may be present naming a few bacterial infections, anal fissures, a bowel obstruction, or Crohn's disease. There isn't sufficient information to reach a specific diagnosis. I would advise you to visit a general surgeon so that you can be examined and undergo the necessary investigations such as a colonoscopy, stool examination, etc. to find the underlying cause of the problem and have it treated accordingly. If the problem persists or worsens visit the general surgeon at the earliest